(CNSNews.com) – Though trailing in third place behind two other GOP rivals, Republican presidential candidate Rick Santorum is in a near dead heat in a head to head match-up with President Barack Obama, a Rasmussen Reports survey finds.

In the potential contest, Obama beats Santorum, a former Pennsylvania senator, 46 percent to 44 percent.

Still, Santorum is a distant third in RealClearPolitics average of national polls of Republican candidates, running more than a dozen percentage points behind both former House Speaker Newt Gingrich and former Massachusetts Gov. Mitt Romney.

Obama leads Romney by just one point, 46 percent to 45 percent. Obama and Romney have been virtually tied in various polls for months. Gingrich, a former House speaker, does the worst in a head to head matchup, trailing Obama by eight points, 49 percent to 41 percent. Meanwhile Texas Rep. Ron Paul has a respectable showing, trailing Obama by just three percentage points, 45 percent to 42 percent.

The Rasmussen daily tracking poll for Thursday was of 500 voters.

In what has been a hotly contested Republican primary so far, Romney has won the New Hampshire and Florida primaries by comfortable margins, Santorum narrowly won the Iowa caucus and Gingrich convincingly won the South Carolina primary.

In a positive sign for Republicans, the Rasmussen poll found that “the number of Americans who call themselves Democrats has fallen to a record low,” with 35.9 percent identifying themselves as Republicans and 32.5 percent identifying themselves as Democrats. The same poll also shows that Obama has a 47 percent overall job approval rating.

The next GOP contests are in Nevada and Maine this Saturday.

In Nevada, Romney leads by 20 points, with 45 percent to Gingrich’s 25 percent, Santorum with 11 percent and Paul with nine percent, according to a Las Vegas Review-Journal poll taken from Jan. 27-31.

Santorum got a boost this week in the state with the endorsement of Sharon Angle, the GOP candidate for U.S. Senate in 2010. Meanwhile, billionaire Donald Trump said Thursday he is endorsing Romney.

Then on Tuesday, Colorado, Minnesota and Missouri all have nominating contests. Of those states, only Minnesota has had a poll in the last month. A Public Policy Polling survey found that Gingrich leads Romney by 18 points in a poll taken on Jan. 21-22.